Two application rates (9 and 18 t/ha) of poultry litter and a recommended rate of commercial fertilizer were studied to determine their effects on nutrient (N and P) losses in surface and subsurface runoff and loadings in soil layers from conventionally-tilled com plots. The EPIC model was used to simulate surface and subsurface water quality affected by the treatments. The model predicted higher sediment losses than observed data from all treatments. The overpredicted sediment losses resulted in overprediction of organic-N and sediment-P losses in surface runoff. Simulated soluble-P losses in surface runoff were close to observed data, while NO₃-N losses in surface runoff were underpredicted from all treatments. Observed NO₃-N concentrations in leachate at 1.0-m depth from commercial fertilizer treatment were fairly well predicted. But the concentrations were overpredicted from poultry litter treatments due to high simulation of organic-N mineralization simulated by the model.